Flexible load-carrying cord, apparatus and polymeric construction utilizing same

ABSTRACT

A flexible load-carrying cord which is adapted for embedment in a polymeric product, apparatus and method for making such a cord, and product utilizing same are provided wherein the cord comprises a plurality of elements which are twisted in one direction and normally have a tendency to untwist and a polymeric sleeve is bonded around the cord with the sleeve comprising a polymeric matrix having a plurality of discrete randomly arranged fibers embedded therein with the fibers being disposed in a helical pattern which extends in a direction opposite from the one direction and the sleeve with its fibers serving to substantially eliminate the tendency of the elements to untwist.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a flexible load-carrying cord which is adaptedfor embedment in a polymeric construction apparatus and method formaking such cord, and polymeric construction having such cord embeddedtherein.

2. Prior Art Statement

Flexible load-carrying cords comprised of a plurality of twistedelements are widely used in polymeric products or constructions forreinforcement and/or load-carrying purposes by embedding same in theirassociated constructions. However, such cords are generally deficientbecause in some applications they are not capable of being bonded inposition in a tenacious high strength manner and in other applicationsthey tend to become untwisted thereby placing substantial stress onadjoining polymeric material within which they are embedded resulting infailure of the cords, weakening of adjoining polymeric matrix material,and eventual premature failure of the associated polymeric construction.

It is known in the art to provide a polymeric coating or sleeve aroundone or more flexible members to define a structure which may be used forvarious purposes. For example, U.S. Pat. No. 4,183,888 discloses amethod of providing a plastic coating on a heated wire.

It is also known in the art to embed elongate particles or fibers withina polymeric matrix to define a reinforced polymeric structure. Forexample, U.S. Pat. No. 3,657,938 teaches the utilization of elongatedfibers in the load-carrying section of an endless power transmissionbelt and the fibers serve to reinforce the load-carrying section and arearranged substantially in alignment with the endless path of the belt.Similarly, U.S. Pat. No. 4,056,591 teaches a method of orienting fibersfrom the axial direction, particularly in hose formed by extrusion.Finally, it has also been proposed in U.S. Pat. No. 4,057,610 to definea hose comprising extrudable polymer reinforced with discontinuousfibers oriented in the radial direction.

It is an object of this invention to provide an improved flexibleload-carrying cord which is adapted for embedment in a polymericconstruction.

Another object of this invention is to provide an improved apparatus andmethod for making such a cord.

Another object of this invention is to provide an improved polymericconstruction utilizing such cord.

Other aspects, embodiments, objects, and advantages of this inventionwill become apparent from the following specification, claims, anddrawings.

SUMMARY

In accordance with the present invention there is provided an improvedflexible load-carrying cord which overcomes the above-mentioneddeficiencies; and such improved cord is adapted for embedment in apolymeric construction and comprises a plurality of elements which aretwisted in one direction and normally have a tendency to untwist.

In accordance with one embodiment of this invention a polymeric sleeveis bonded around the elements with the sleeve comprising a polymericmatrix having a plurality of discrete randomly arranged fibers embeddedtherein with the fibers being disposed in a helical pattern whichextends in a direction opposite from the one direction; and, the sleevewith its fibers serves to substantially eliminate any tendency of theelements to untwist.

Also provided in accordance with this invention is an improved apparatusand method for making a flexible load-carrying cord of the charactermentioned which is adapted for embedment in a polymeric construction.

This invention also provides an improved construction made primarily ofpolymeric material which has a load-carrying cord of the charactermentioned embedded in at least a portion thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show present preferred embodiments of thisinvention, in which

FIG. 1 is a fragmentary view with parts broken away illustrating oneexemplary embodiment of a flexible load-carrying cord of this invention;

FIG. 2 is a view with parts in cross section, parts in elevation, andparts broken away illustrating one exemplary embodiment of an apparatusand method for making the cord of FIG. 1;

FIG. 3 is a view taken essentially on the line 3--3 of FIG. 2;

FIG. 4 is a view in elevation of a pair of die components comprising theapparatus of FIG. 2 and illustrating such components exploded apart;

FIG. 5 is a view with parts in cross section, parts in elevation, andparts broken away illustrating another exemplary embodiment of anapparatus and method which may be used in making the cord of FIG. 1;

FIG. 6 is a fragmentary cross-sectional view of a conveyor beltconstruction which utilizes a load-carrying cord of this invention;

FIG. 7 is a cross-sectional view of an endless power transmission beltwhich also utilizes a load-carrying cord of this invention in itsload-carrying section;

FIG. 8 is a view similar to FIG. 7 of an endless power transmission beltwhich utilizes a modification of the load-carrying cord of thisinvention; and

FIG. 9 is a cross-sectional view illustrating a pneumatic tireconstruction which also utilizes a load-carrying cord of this invention.

DETAILED DESCRIPTION

Reference is now made to FIG. 1 of the drawings which illustrates oneexemplary embodiment of a flexible load-carrying cord of this inventionwhich is designated generally by the reference numeral 20 and such cord20 is particularly adapted for embedment in a polymeric construction ofany suitable type known in the art and typical constructions will bedescribed subsequently. The cord 20 comprises a plurality of elementseach designated by the reference numeral 21 which are twisted in onedirection as indicated by the arrow 22 and usually such elements arehighly twisted and have a normal tendency to untwist, particularly afterthe elements 21 are embedded in an associated polymeric matrix. Inaccordance with the teachings of this invention the cord 20 has apolymeric sleeve, designated generally by the reference numeral 23,bonded around the twisted elements 21 and such sleeve is of uniqueconstruction and will now be described in detail.

The sleeve 23 is comprised of a polymeric matrix 24 and has a pluralityof discrete randomly arranged fibers embedded therein and arepresentative few of such fibers will be designated by the samereference numeral 25. The fibers 25 are disposed in a helical patternwhich extends in a direction 26 which is opposite from the direction 22in which the elements 21 are twisted; and, the sleeve 23 with its fibers25 serves to substantially eliminate any tendency for the elements 21 tountwist.

Any desired member, of elements 21 may be used in a cord 20 and suchelements may be made of metallic material, such as steel, ornon-metallic material including either a natural or synthetic material.Examples of synthetic materials which may be employed include nylon,polyaramid, polyester, and the like.

The sleeve 23 is comprised of a polymeric matrix 24 as previouslymentioned and such matrix may be any suitable composition known in theart including either a natural or synthetic material; and, preferablythe polymer comprising the matrix 24 is a rubber compound.

The fibers 25 comprising the sleeve 23 may also be of any suitablematerial known in the art, including metallic and nonmetallic material;and, such fibers are preferably nonmetallic fibers made of either anatural or synthetic material. Each of the fibers 25 preferably has adiameter ranging between 0.001 and 0.050 inch and a length rangingbetween 0.001 and several inches with the preferred length being roughly1/4 of an inch.

The sleeve 23 is preferably comprised of between 5 and 50 parts byweight of fibers for each one hundred parts of polymer defining thematrix material 24. Further, the polymeric matrix 24 may be providedwith other constituents including one or more of items such as, afiller, plasticer, antidegradant, processing aid, curative, bondingagent, and the like. The particular items selected for a polymericmatrix will vary depending upon the weight and type of polymer and thetype and weight of fibers used.

The cord 20 as illustrated in FIG. 1 may be substantially fully curedbefore embedment in its polymeric construction. However, it ispreferable that the cord 20 be uncured or only partially cured beforeembedment whereupon such uncured or partially cured cord is then finallycured together with its polymeric construction.

Having described the cord 20 of this invention, reference is now made toFIG. 2 of the drawings which illustrates one exemplary embodiment of anapparatus and method for making the cord and such apparatus and methodare designated generally by the reference numeral 30. A description ofthe apparatus and method will now be presented and the same referencenumerals will be used for constituents or components of the cord 20during making thereof as were used in the completed cord describedabove.

The apparatus 30 comprises means for twisting a plurality of elements 21in one direction and such twisting means is designated schematically byarrows 31 at the left and right ends of the illustration of FIG. 2; and,it will be appreciated that the elements 21 (after having been twistedby the twisting means 31) normally have a tendency to untwist. Theapparatus 30 also has means for moving and tensioning the twistedelements 22 and such moving and tensioning means are designatedschematically by double arrows 32 at each end of FIG. 2.

The apparatus 30 also has means 33 for forming a flowable polymericmatrix material 24 which has a plurality of discrete randomly arrangedfibers 25 embedded therein to define the polymeric sleeve 23 having thefibers disposed in the previously described helical pattern extending inthe direction 26 which is opposite from the direction 22 in which theelements 21 are twisted. The apparatus also has means 34 for bonding thesleeve concentrically around and against the elements during movement ofsuch elements by the moving means 32 so that upon curing the sleeve 23the fibers 25 serve to substantially eliminate any tendency for theelements 22 to untwist and as previously mentioned.

The forming means 33 and bonding means 34 in this example of theinvention are defined as an extrusion die which is designated generallyby the reference numeral 35. The die 35 is provided for extrudingtherethrough flowable material 24 with its embedded fibers 25 to definethe sleeve 23 having the helical pattern in such fibers. The extrusiondie 35 operates to define the sleeve concentrically around and bondedagainst the elements 21.

The die 35 is a stationary die and has integral means therein fordefining the helical pattern in the fibers 25. In particular, and asillustrated in FIGS. 2, 3 and 4 of the drawings, the die 35 comprises aninner die component 36 which has an outside substantially frustoconicalsurface 37 and a cooperating outer die component 40 which has an insidesubstantially frustoconical surface 41. The previously mentionedintegral means in the die 35 comprises curved means associated with thesurfaces 37 and 41 and in this example such curved means comprisesgroove means.

In particular, the groove means comprises a plurality of curved grooves,each designated by the same reference numeral 43, extending into theinner die component 36 from its frustoconical outside surface 37; and,as will be apparent from FIG. 3 of the drawings the grooves 43 aredisposed in equal angularly spaced relation having an angle 44therebetween of roughly 45°. The groove means also comprises a pluralityof curved grooves, each designated by the reference numeral 45,extending in the outer die component 40 from its frustoconical insidesurface 41. The curved grooves 45 in the component 40 are also disposedin equal angularly spaced relation with an angle of roughly 45°therebetween and it will be seen, typically at 47 in FIG. 3, that eachgroove 45 in the outer component is disposed substantially midwaybetween a pair of grooves 43 in the inner component 36 with the diecomponents 36 and 40 in assembled relation.

The extrusion die 35 of the apparatus 30 has means 50 for spacing thedie components 36 and 40 to define a substantially frustoconical volume51 therebetween; and, the volume 51 has a substantially radial thickness52 which is roughly equal to the thickness of the sleeve 23. The spacingmeans 50 in this example of the invention comprises a plurality ofspacing members 53 and associated threaded screws 54; and, a typicalspacing member 53 is illustrated in FIG. 2 together with a typicalthreaded screw 54.

Each spacing member 53 is held in position by an associated threadedscrew 54 which extends through an opening 55 in the outer die component40 and through an aligned opening 56 in the spacing member 53. Thethreaded inner end portion of the threaded screw 54 is threaded within ablind threaded opening 57 in the inner die component 36. The dimensionalthickness of the spacing members 53 is precisely controlled to defineany desired thickness for the sleeve 23; and, each spacing member maycomprise a plurality of precise washer-like components which aredisposed in stacked relation until the desired thickness is achieved.

The apparatus 30 also has means 59 for supplying the flowable polymericmaterial 24 into the frustoconical volume 51 from an associated extruderwhich is designated schematically by an arrow 60. The means 59 comprisesa high pressure conduit 61 which is suitably held in sealedcommunication (by welds, or the like) in a sealing ring structure 62associated with the large diameter end of the frustoconical volume 51.The outer end of the conduit 61 is in flow communication with theextruder 60.

The apparatus and method 30 may also utilize suitable means to providepartial precuring of the polymeric matrix material 24 with the fibers 25therein disposed in their helical pattern, and as previously described;and, such precuring means may be in the form of a curing apparatus 63.The apparatus 63 may be used to provide generally of the order of 10 to20% partial precuring of the polymeric sleeve 23. The resulting cord 20may then be embedded in an associated polymeric construction, of thetype to be subsequently described. In the case of an uncured orpartially cured sleeve 23, final curing for such sleeve 23 takes placeduring final curing of the polymeric construction within which the cord20 is used. The apparatus 63 may be any suitable curing apparatus knownin the art including a microwave curing apparatus, or an apparatus whichprovides curing by steam or hot air at controlled temperatures andpressures.

In those applications in which the sleeve 23 is uncured or onlypartially cured and the associated cord 20 is not used immediately suchsleeve is preferably dusted with a suitable powder in order to renderits outside surface less tacky and enable easier handling of the overallcord and coiling thereof on a supply spool, for example. The powder maybe any suitable powdered fatty acid or fatty acid salt and examples ofsame include zinc stearate, zinc oleate, or the like.

It will also be appreciated that instead of the apparatus 63 providingonly partial curing of the sleeve 23, it may provide substantially fullcuring thereof. In this instance the composition of the sleeve 23 ispreferably such that it will be tenaciously bonded within the polymericconstruction in which it is embedded as a load-carrying componentthereof.

Another exemplary embodiment of the apparatus and method of thisinvention is illustrated in FIG. 5 of the drawings. The apparatus andmethod of FIG. 5 are substantially identical to the apparatus and methodpreviously described and thus will be designated by the same referencenumeral 30 as before; and, components of the apparatus of FIG. 5 whichare similar to previously described components have also been designatedby the same reference numerals as before. Only those components whichare substantially different from corresponding components of thepreviously described apparatus 30 will be designated by a new referencenumeral and described in detail.

The apparatus of FIG. 5 comprises the twisting means 31, the moving andtensioning means 32, and the means 59 for supplying the polymericmaterial 24 from an extruder 60, essentially as previously described.However, it will be seen that instead of the extrusion die (which isprovided for forming and bonding flowable polymeric matrix material)being a stationary die such die is a rotatable die and is designatedgenerally by the reference numeral 65. The rotatable die 65 has anannular orifice 66 provided in the structural components thereof and theorifice 66 is sized to align the fibers 25 substantially parallel to thelongitudinal axis of the die 65 which coincides with the centrallongitudinal axis 67 of the elements 21 upon extruding therethrough thepolymeric matrix 24 with its embedded fibers 25. It will be appreciatedthat if the die 65 were to be maintained stationary, i.e., not rotated,the fibers 25 of the sleeve 23 would remain substantially parallel tothe axis 67 in the completed cord 20.

However, the apparatus 30 has means 70 for rotating the rotatable die 65during movement of the twisted elements 21 in their rectilinear path asproduced by the moving means 32 to thereby dispose the fibers 25 in ahelical path during the defining and bonding of the sleeve against theelements 21, and such helical path extends in the direction 26 (aspreviously described) which is opposite from the direction 22 in whichthe elements 21 are twisted by the twisting means 31.

The rotating means 70 comprises a ring gear 71 which is fixed around therotatable die 65 and a spur gear 72 which is adapted to engage androtate the ring gear 71 and die 65. The spur gear 72 is driven by amotor 73 which is connected thereto by a mechanical connection 74.

Having described the improved load-carrying cord 20 of this inventionand two embodiments of an exemplary apparatus and method for making sucha cord, reference is now made to FIGS. 6, 7, 8, and 9 for presentationsof typical exemplary embodiments of polymeric constructions which havethe improved load-carrying cord 20 provided in at least a portion ofeach construction.

The cord 20 is illustrated in FIG. 6 embedded in a central portion of apolymeric construction defined as a belt conveyor 76. The belt conveyor76 is made primarily of a polymeric matrix material 77 in the form ofrubber and the cord 20 is a helically wound load-carrying cord.

FIG. 7 illustrates the load-carrying cord 20 provided in an endlesspower transmission belt 80. The belt 80 comprises a tension section 81,a load-carrying section 82, and a compression section 83; and, the cord20 is provided as a helically wound cord and as an integral part of theload-carrying section 82. The cord 20 is embedded in a suitable gumcushion 84 of the load-carrying section 82.

The polymeric construction of FIG. 8 is also an endless powertransmission belt which again is designated by the general referencenumeral 80. The belt 80 of FIG. 8 has a tension section 81, aload-carrying section 82, and a compression section 83 which is providedwith a load-carrying cord 20. The load-carrying cord 20 is alsohelically wound; however, such cord has a sleeve 23 which is of largeradial thickness 85. The large radial thickness 85 is such that it isnot necessary to embed the cord 20 in the usual cord cushion. Instead,the sleeve 23 serves the multiple purpose of holding the twistedelements 21 in position so as to prevent untwisting thereof as well asdefining the cord cushion.

The polymeric construction of FIG. 9 is in the form of a pneumatic tirewhich is designated generally by the reference numeral 86. For ease ofpresentation, the tire 86 is shown as a simplified structure which ismade primarily of a rubber matrix material 87 and is shown withoutreinforcing fabrics, and the like, usually comprising such a tire. Thecord 20 is provided adjacent the tire tread and in each tire bead asshown at 100 and 101 respectively.

The polymeric constructions illustrated in FIGS. 6, 7, 8, and 9 in eachinstance have been shown by cross hatching as being made of polymericmaterial in the form of rubber; however, it is to be understood that anysuitable polymeric material may be employed including not only rubberbut synthetic plastic material as well.

It should be emphasized that in making the various polymericconstructions illustrated in FIGS. 6, 7, 8, and 9 the improvedload-carrying cord of this invention is in each instance preferablydisposed in the polymeric construction while the cord 20 is in asubstantially uncured or only partially cured condition. However, itwill be appreciated that the cord 20 may be completely cured, ifdesired, before disposal in an associated polymeric construction.

The radial thickness of the sleeve 23 provided around the twistedelements 21 of a cord 20 may vary depending on the application. Forexample, a bundle of twisted elements 21 having an outside diameter of0.150 inch may have a sleeve 23 which has a radial thickness rangingbetween roughly 0.010 and 0.100 inch.

The cord 20 may be used to define an associated polymeric construction,such as the previously described constructions of FIGS. 6 through 9 in acontinuous process immediately after extruding the sleeve 23concentrically around and against the twisted elements 21. However, inmany instances the cord 20 with its uncured sleeve may be coiled on anassociated spool to define a supply spool or roll thereof after passingsame through a dusting chamber containing a powdered fatty acid or fattyacid salt as mentioned earlier.

As indicated above, the sleeve 23 is comprised of various items orcomponents of the character previously described; and, such componentsinclude suitable bonding material. The particular bonding materialemployed will vary depending upon the material used to define theelements 21 and the other components of the sleeve 23. However, suchbonding material may be a cobalt II complex, elemental sulphur, zincoxide, a resorcinolic (or phenolic or complex of the two) resin, amethylene donor resin, silica, or other materials known in the art toenhance the adhesion of a polymeric or rubber sleeve to a cord corecomprised of twisted elements 21.

While present exemplary embodiments of this invention, and methods ofpracticing the same, have been illustrated and described, it will berecognized that this invention may be otherwise variously embodied andpracticed within the scope of the following claims.

What is claimed is:
 1. In a flexible load-carrying cord which is adaptedfor embedment in a polymeric construction said cord comprising aplurality of elements which are twisted in one direction and normallyhave a tendency to untwist, the improvement comprising a polymericsleeve bonded around said elements, said sleeve comprising a polymericmatrix having a plurality of discrete randomly arranged fibers embeddedtherein, said fibers being disposed in a helical pattern which extendsin a direction opposite from said one direction, and said sleeve withits fibers serving to substantially eliminate said tendency of saidelements to untwist.
 2. A cord as set forth in claim 1 in which saidelements are made of metallic material.
 3. A cord as set forth in claim1 in which said elements are made of non-metallic material.
 4. A cord asset forth in claim 3 in which said non-metallic material is polymericmaterial.
 5. A cord as set forth in claim 1 in which each of said fibershas a diameter ranging between 0.001 and 0.050 inch and a length rangingbetween 0.001 and several inches.
 6. A cord as set forth in claim 5 inwhich said fibers are made of non-metallic material.
 7. A cord as setforth in claim 6 in which said fibers comprise between 5 and 50 parts byweight for each 100 parts of polymer defining said matrix material.
 8. Acord as set forth in claim 7 in which said polymer is rubber and saidfibers are organic fibers.
 9. In a construction made primarily ofpolymeric material and having a flexible load-carrying cord embedded inat least a portion thereof, said cord comprising a plurality of elementswhich are twisted in one direction and normally have a tendency tountwist, the improvement comprising a polymeric sleeve bonded aroundsaid elements and defining the outer part of said cord, said sleevecomprising a polymeric matrix having a plurality of discrete randomlyarranged fibers embedded therein, said fibers being disposed in ahelical pattern which extends in a direction opposite from said onedirection, and said sleeve with its fibers serving to substantiallyeliminate said tendency of said elements to untwist.
 10. A constructionas set forth in claim 9 defined as a power transmission belt whereinsaid portion is a load-carrying section of said belt and saidload-carrying cord is embedded in said load-carrying section.
 11. Aconstruction as set forth in claim 10 in which said polymeric sleeve isof substantial thickness and serves as a cushion for said elements ofsaid cord.
 12. A construction as set forth in claim 10 defined as a beltconveyor wherein said portion is a central load-carrying portion of saidbelt conveyor.
 13. A construction as set forth in claim 10 defined as apneumatic tire wherein said portion is a load-carrying portion of saidtire.